[Python-Dev] Challenge: Please break this! (a.k.a restricted mode revisited)

[Wes Turner]

On Apr 10, 2016 11:51 AM, "Jon Ribbens" <jon+python-dev at unequivocal.co.uk>
wrote:
>
> On Sun, Apr 10, 2016 at 02:51:23PM +1000, Nick Coghlan wrote:
> > On 9 April 2016 at 22:43, Victor Stinner <victor.stinner at gmail.com>
wrote:
> > > See pysandbox test suite for a lot of ways to escape a sandbox.
CPython has
> > > a list of know code to crash CPython (I don't recall the dieectory in
> > > sources), even with the latest version of CPython.
> >
> > They're at https://hg.python.org/cpython/file/tip/Lib/test/crashers
>
> Thanks. I take your point that sandboxing Python requires CPython to
> free of code execution bugs. However I will note that none of the
> crashers in that directory will work inside my experiment (except
> "infinite_loop_re.py", which isn't a crasher just a long loop).
>
> > Even without those considerations though, there are system level
> > denial of service attacks that untrusted code can perform without even
> > trying to break out of the sandbox - the most naive is "while 1:
> > pass", but there are more interesting ones like "from itertools import
> > count; sum(count())", or even "sum(iter(int, 1))" and "list(iter(int,
> > 1))".
>
> Yes, of course. I have already explicitly noted that infinite loops
> and memory exhausation are not preventable.
>
> > Operating system level security sandboxes still aren't particularly
> > easy to use correctly, but they're a lot more reliable than language
> > runtime level sandboxes, can be used to defend against many more
> > attack vectors, and even offer increased flexibility (e.g. "can write
> > to these directories, but no others", "can read these files, but no
> > others", "can contact these IP addresses, but no others").
>
> I don't entirely trust operating system sandboxes either - I generally
> assume that if someone can execute arbitrary code on my machine, then
> they can do anything they want to that machine.
>
> What I *might* trust, though, would be a "sandbox Python" that is
> itself running inside an operating system sandbox...
>

* https://github.com/jupyter/jupyterhub/wiki/Spawners
  - Docker LXC Containers
  - https://github.com/jupyter/jupyterhub/wiki/Authenticators
    - DOS is still trivial
    - Segfault is still trivial
* http://doc.pypy.org/en/latest/sandbox.html#introduction
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